Title of Invention

A METHOD OF MANUFACTURING A STEERING RACK FOR A VEHICLE AND PINION STEERING GEAR

Abstract A stocking lack for a vehicle rock and pindon sterring geur and a method of manufacture theroof. The according rack comprising a first member having a toothed region, attached to a tublar second member. The second member having at least loast one region of incrensed wait thickness and reduced bore diarector formed by an opning operations.
Full Text 1
COMPOSITE STEERING RACK
TECHNICAL FIELD
5 The present invention relates to steering racks for vehicle rack and pinion steering
gears, and more particularly to such racks manufactured by attaching a tubular
member to a toothed member.
BACKGROUND
10
Most vehicle steering racks are manufactured from round solid bar stock, with the
toothed region broachad across the bar near one end This results in the cross
section of the toothed region having a 'D' shape and hence these racks are commonly
referred to as "D-racks". The toothed region of stich a broached D-rack has
15 significantly flss bending strength than the round solid shank extending from it.
However, to minimise the "weight of the steering rack, it is desirable that the toothed
region and the shank have similar bending strength. A common approach to this
problem is to gun drill the shank over most of its length resulting in a substantially
tubular shank. However, the disadvantages of gun drilling are that material is wasted
20 and it is a relatively expensive process.
An alternative method of manufacturing a steering rack from round solid bar stock is
to forge the toothed region. US Patents 4,571,982 (Bishop) and 5,862.701 (Bishop at
al) disclose die apparatus for flashless warm forging the toothed region to net shape.
35 "Net shape" means that the forged rack testh do not require any further machining
after forging. An advantage of forging is that the rack teeth may be shaped to have a
variable gear ratio. The cross section of the toothed region of racks forged by this
type of die has a 'Y' shape and such racks are commonly referred to as "Y-racks".
The toothed region of a forged Y-rack has greater bending strength than the toothed
30 region of a D-rack broached from the same diameter solid bar, and so Y-racks can be
forged from smaller diameter bar whilst maintaining overalI bending strength.
However, the shanks of Y-racks are still commonly gun drilled to further reduce
weight.

2
Numerous attempts have been made to further reduce weight by the manufacture of
hollow steering racks from tube stock. One such method used in limited production is
disclosed in US Patent 4,598,451 (Takanosuke) where a series of mandrels is passed
5 through a flattened tube to progressively fill an external tooth die. This method is
expensive and time consuming and as such is not suited to high volume production.
Furthermore, the size of teerth that can be produced is limited by the wall thickness of
the tube and the method is not stilted to producing racks with variable ratio teeth.
10 A "composite rack" is defined as a rack made by joining two or more members to
each other. Typically a composite rack is made by joining 3 shank made from tube to
a short solid rack member. Such composite racks have the advantages of reduced
weight without the limitations of forming the rack teeth onto a tube. Various methods
of making composes racks have been proposed or used in limited production. For
15 example, a composite steering rack has been used in Honda "Odyssey" vehicles, This
rack is made by welding a tubular shank to a short solid forged D-rack. Typically,
steering racks for hydraulic power steering gears have an external circumferential
groove approximately mid way along the shank for locating a hydraulic platan. A
disadvantage of the Honda "Odyssey" rack is that since the tubular shank has a
20 constant wait thickness along its length, the wall must be thick enough to machine this
groove on its outside diameter without wealening the rack. The wait of the tube must
also be thick enough to machine an internal thread at one end to attach a tie rod end.
These localised limitations on wall thickness mean that a composite rack having a
tubular shank of constant wall thickness cannot fully exploit the weight saving
25 potential of a composite rack.
The present invention seeks to ameliorate at Ieast some of the disadvantages of the
prior art.
30 SUMMARY OF INVENTION
In a first aspect the present invention consists of a steering rack for a vehicle rack and
pinion steering gear, comprising a first member having a toothed region, attached to a

3
tubular second member, characterised in that said second member has at least one
region of increased wall thickness and reduced bore diameter formed by an upsetting
operation.
5 Preferably, said region of increased wall thickness and the portions of said second
member immediately adjacent thereto have substantially the same outside diameter.
Preferably, said region of increased well thickness has an external circumferential
groove.
10
Preferably, said upsetting operation is performed prior to attaching said first and
second members to each other.
Preferably, said first and second members are attached to each other by a welding
15 operation.
Preferably, said first member is substantially solid.
Preferably, said toothed region is flashless warm forged.
20
In a second aspect the present invention consists of a method of manufacturing a
steering rack for a vehicle rack and pinion steering gear comprising the steps of
(I) forging a blank to form a first member having a toothed region; and
25
(Il) attaching said first member to a tubular second member by a welding operation;
characterised in that said second member is manufactured by performing an
upsetting operation on a tube such that said second member has at least one region
30 of increased wall thickness and reduced bore diameter.
Preferably, said upsetting operation does not substantially alter the outside diameter
of said tube.

4
Preferably, supsequent to said upsetting operation, a circumferential groove is
machined in the outside diameter of said region of increased wall thickness.
5 Preferably, said forging comprises flashless warm forging.
Preferably, prior to step (lI). the ends of said first membar are finished machined.
Preferably, prior to step (ii), said toothed region is induction hardened.
10
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a perspective view of a composite steering rack in accordance with the
present invention.
15
Fig. 2 is a cross sectional view of the forged rack tooth member of the rack shown in
Fig. 1.
Fig, 3 is a cross section through III-III of the forged rack tooth member shown in Fig,
20 2.
Fig. 4 is a cross sectional view of the tublar shank member of the rack shown in Fig.
1.
25 BEST MODE OF CARRYING OUT THE INVENTION
Fig, 1 depicts a composite steering rack 1 in accordance with the present invention
comprising a forged rack tooth member 2 and a tubular shank member 3, Tooth
member 2 has a toothed region 4 over a substantiaI length thereof, a tie rod end 5
30 with an internal thread for attaching a tie rod, and a joint end 6 at the opposite end
thereof.

5
Tooth member 2 is flashless warm forged from a solid cylindrical blank (not shown) in
a die apparatus similar to that diseased in US Patents 4,571,982 (Bishop) and
5,862,701 (Bishop et al). Toothed region 4 is forged to net shape and the teeth
thereon do not require any further machining. The cross section of toothed region 4
5 has a 'Y' shape as shown in Fig. 3. Once tooth member 2 has been warm farged,
toothed region 4 is subsequently induction hardened. The ends of tooth member 2 are
left soft to allow for machining to produce tie rod end 5 and joint end 6, as shown in
Fig. 2. Joint end 6 is machined to have a protruding annular form similar in outside
and inside diameters to the joint end 7 of tubular shank member 3. An air bleed port 9
10 is drillad through end 6 to provide a vent passage for air to pass through the bore of
tubular shank number 3.
Tubular shank member 3 is manufactured from a length of tube (not shown) of
constant diameter and wait thickness. Referring to Fig. 4, tubular shank member 3
15 has the same constant wall thickness and outside diameter as the tube along its
length except for regions 10 and 12. which have increased wall thickness and
reduced bare diameter formed by localised upsetting operations. Thickened region 12,
has increased wail thickness 13 and a circumferential groove 14 machined on its
outside diameter to locate a hydraulic piston (not shown). The outside diameter of
20 thickened region 12 is substantially unaltered by the upsetting operation and as such
the outside diameter of thickened region 12 is substantially the same as the portions
21 of tubular shank member 3 immediately adjacent thereto. Since circumferential
groove 14 is in a region of increased wall thickness it does not weaken tubular shank
member 3.
25
Thickened region 10 is at one end of tubular shank member 3 and has an internal
thread 8 machined therein for attaching a tie rod end. Unlike thickened region 12, the
outside diameter of thickened region 10 is reduced by the upsetting opevation.
30 The localised thickening provided by the upsetting operations clearly allows tubular
shank member 3 to be manufactured from a thinner wall tube than would otherwise
be required if tubular shank member was of constant wall thickness. For example, a
rack having a shank outside diameter of apprcodmately 26mm may be made in

6
accordance with the present invention by upsetting a tube having a wall thickness of
approximately 4mm. This tube may be upset to increase the wall thickness to, for
example, approximately 5.5mm in thickened region 12 to provide sufficient strength
once groove 14 is machined. A shank made from tube without upsetting would require
5 a wall thicknees of at least 5.5mm along its length to provide the same strength at the
region of groove 14, and hence such as rack would be significantly heavier than one
made in accordance with the present invention,
The upsetting operation may be performed by locally heating the tube and then axlally
10 compressing it whilst restraining the outside diameter of the tube by rollers or the like.
By restraining the outside diameter, the tubs is upset inwardly thereby increasing the
wall thickness and reducing the bore diameter at regions 10 and 12.
Subsequent to tooth member 2 and tubular shank member 3 being manufactured as
15 described above, they are attached to each other by a welding operation. Joint end 6
of tooth member 2 is welded to joint end 7 of tubular shank member 3, preferably by a
magnetic arc, friction or laser welding process. Once voiding has taken place, any
external excess weld seam may be removed in a conventional manner. A stress
relieving operation may then be carried out on the weld. The integrity of the weld may
20 be checked by a crack detection operation. After welding, tubular shank member 3
may be induction hardened and ground to finished size.
To minimise bending and misalignment during the welding operation, the tooth
member and tubular shank member are clamped in a fixture and the welding
25 operation is fully automated. The welding may be controlled to an extent that
subsequent straightening operations are not raquired.
Whilst the embodiment described above utilises a 'Y' shaped tooth member, it should
be understood that tooth members of other forms may be used, such as 'D' shaped
30 tooth members. It should also be understood that the tooth member may be made by
a machining operation, such as broaching, instead of forging. Furthermore, the teeth
of the tooth member may have either a constant ratio or variable ratio form

7
CLAIMS
1. A steering rack for a vehicle rack and pinion steering gear, comprising a first
member having a toothed region, attached to a tubular second member,
5 characterised in that said second member has at least one region of increased
wall thickness and reduced bore diameter formed by an upsetting operation.
2. A steering rack as claimed in claim 1 wherein said region of increased walI
thickness and the portions of said second member immediately adjacent thereto
10 have substantially the same outside diameter.
3. A steering rack as claimed in claim 1 wherain said-region of incased wait
thickness has an external circumferential groove.
15 4. A steering rack as claimed in claim 1 wherein said upsetting operation is
performed prior to attaching said first and second members to each other.
5. A steering rack as claimed in claims 1 or 4 wherein said first and second members
are attached to each other by a welding operation.
20
6. A steering rack as claimed in claim 1 wherein said first member is substantially
solid.
7. A steering rack as claimed in claim 5 wherein said toothed region is flashless
25 warm forged.
8. A method of manufacturing a steering rack for a vehicle rack and pinion steering
gear comprising the steps of
30 (I) forging a blank to form a first member having a toothed region; and
(II) attaching said first member to a tubular second member by a welding
operation;

8
characterised in that said second member is manufactured by performing an
upsetting operation on a tube such that said second member has at feast one
region of increased wall thickness and reduced bore diameter.
5
9. A method of manufacturing a steering rack as claimed in claim 8 wherein said
upsetting operation does not substantially after the outside diameter of said tube,
10. A method of manufacturing a steering rack as claimed in claim 8 wherein
10 subsequent to said upsetting operation, a circumferential groove is machined in
the outside diameter of said region of increased wall thickness.
11. A method of manufacturing a steering rack as claimed in claim 8 wnerain said
forging comprises flashless warm forging.
15
12. A method of manufacturing a steering rack as claimed in claim 8 wherein prior to
step (II), the ends of said first member are finished machined.
13. A method of manufacturing a steering rack as claimed in claim 8 wherein prior to
20 step (ii), said toothed region is induction hardened.

A stocking lack for a vehicle rock and pindon sterring geur and a method of manufacture theroof. The according rack
comprising a first member having a toothed region, attached to a tublar second member. The second member having at least loast one
region of incrensed wait thickness and reduced bore diarector formed by an opning operations.


Documents:

00543-kolnp-2006-abstract.pdf

00543-kolnp-2006-claims.pdf

00543-kolnp-2006-description complete.pdf

00543-kolnp-2006-drawings.pdf

00543-kolnp-2006-form 1.pdf

00543-kolnp-2006-form 3.pdf

00543-kolnp-2006-form 5.pdf

543-KOLNP-2006-(28-08-2012)-CORRESPONDENCE.pdf

543-KOLNP-2006-ABSTRACT 1.1.pdf

543-KOLNP-2006-ASSIGNMENT.1.3.pdf

543-kolnp-2006-assignment.pdf

543-KOLNP-2006-CORRESPONDENCE.1.3.pdf

543-kolnp-2006-correspondence.pdf

543-KOLNP-2006-DESCRIPTION (COMPLETE) 1.1.pdf

543-KOLNP-2006-DRAWINGS 1.1.pdf

543-KOLNP-2006-EXAMINATION REPORT REPLY RECIEVED.pdf

543-KOLNP-2006-EXAMINATION REPORT.1.3.pdf

543-KOLNP-2006-FORM 1-1.1.pdf

543-KOLNP-2006-FORM 18.1.3.pdf

543-kolnp-2006-form 18.pdf

543-KOLNP-2006-FORM 2.pdf

543-KOLNP-2006-FORM 3-1.1.pdf

543-KOLNP-2006-FORM 3.1.3.pdf

543-KOLNP-2006-FORM 5-1.1.pdf

543-KOLNP-2006-FORM 5.1.3.pdf

543-KOLNP-2006-FORM-27.pdf

543-KOLNP-2006-GPA.1.3.pdf

543-kolnp-2006-gpa.pdf

543-KOLNP-2006-GRANTED-ABSTRACT.pdf

543-KOLNP-2006-GRANTED-CLAIMS.pdf

543-KOLNP-2006-GRANTED-DESCRIPTION (COMPLETE).pdf

543-KOLNP-2006-GRANTED-DRAWINGS.pdf

543-KOLNP-2006-GRANTED-FORM 1.pdf

543-KOLNP-2006-GRANTED-FORM 2.pdf

543-KOLNP-2006-GRANTED-LETTER PATENT.pdf

543-KOLNP-2006-GRANTED-SPECIFICATION.pdf

543-kolnp-2006-international search report.pdf

543-KOLNP-2006-OTHERS.1.3.pdf

543-KOLNP-2006-OTHERS.pdf

543-KOLNP-2006-PETITION UNDER RULE 137-1.1.pdf

543-KOLNP-2006-PETITION UNDER RULE 137.pdf

543-KOLNP-2006-REPLY TO EXAMINATION REPORT.1.3.pdf

abstract-00543-kolnp-2006.jpg


Patent Number 247888
Indian Patent Application Number 543/KOLNP/2006
PG Journal Number 22/2011
Publication Date 03-Jun-2011
Grant Date 30-May-2011
Date of Filing 07-Mar-2006
Name of Patentee BISHOP INNOVATION LIMITED
Applicant Address 10 WATERLOO ROAD NORTH RYDE NSW 2113 AUSTRALIA
Inventors:
# Inventor's Name Inventor's Address
1 ROESKE KLAUS JUEROEN 7 BEECH PLACE LUGARNO NSW 2210 AUSTRALIA
PCT International Classification Number B62D3/12; F16H19/04; B62D3/00
PCT International Application Number PCT/AU2004/001287
PCT International Filing date 2004-09-22
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 2003905204 2003-09-23 Australia